// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Diagnostics.CodeAnalysis;
 
namespace System.ComponentModel.DataAnnotations
{
    /// <summary>
    ///     Allows overriding various display-related options for a given field. The options have the same meaning as in
    ///     BoundField.
    /// </summary>
    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
    public class DisplayFormatAttribute : Attribute
    {
        private readonly LocalizableString _nullDisplayText = new LocalizableString(nameof(NullDisplayText));
 
        /// <summary>
        ///     Default constructor
        /// </summary>
        public DisplayFormatAttribute()
        {
            ConvertEmptyStringToNull = true; // default to true to match behavior in related components
 
            HtmlEncode = true; // default to true to match behavior in related components
        }
 
        /// <summary>
        ///     Gets or sets the format string
        /// </summary>
        public string? DataFormatString { get; set; }
 
        /// <summary>
        ///     Gets or sets the string to display when the value is null, which may be a resource key string.
        ///     <para>
        ///         Consumers should use the <see cref="GetNullDisplayText" /> method to retrieve the UI display string.
        ///     </para>
        /// </summary>
        /// <remarks>
        ///     The property contains either the literal, non-localized string or the resource key
        ///     to be used in conjunction with <see cref="NullDisplayTextResourceType" /> to configure a localized
        ///     name for display.
        ///     <para>
        ///         The <see cref="GetNullDisplayText" /> method will return either the literal, non-localized
        ///         string or the localized string when <see cref="NullDisplayTextResourceType" /> has been specified.
        ///     </para>
        /// </remarks>
        /// <value>
        ///     The null display text is generally used as placeholder when the value is not specified.
        ///     A <c>null</c> or empty string is legal, and consumers must allow for that.
        /// </value>
        public string? NullDisplayText
        {
            get => _nullDisplayText.Value;
            set => _nullDisplayText.Value = value;
        }
 
        /// <summary>
        ///     Gets or sets a value indicating whether empty strings should be set to null
        /// </summary>
        public bool ConvertEmptyStringToNull { get; set; }
 
        /// <summary>
        ///     Gets or sets a value indicating whether the format string should be used in edit mode
        /// </summary>
        public bool ApplyFormatInEditMode { get; set; }
 
        /// <summary>
        ///     Gets or sets a value indicating whether the field should be html encoded
        /// </summary>
        public bool HtmlEncode { get; set; }
 
        /// <summary>
        ///     Gets or sets the <see cref="Type" /> that contains the resources for <see cref="NullDisplayText" />.
        ///     Using <see cref="NullDisplayTextResourceType" /> along with <see cref="NullDisplayText" />, allows the <see cref="GetNullDisplayText" />
        ///     method to return localized values.
        /// </summary>
        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicProperties)]
        public Type? NullDisplayTextResourceType
        {
            get => _nullDisplayText.ResourceType;
            set => _nullDisplayText.ResourceType = value;
        }
 
        /// <summary>
        ///     Gets the UI display string for NullDisplayText.
        ///     <para>
        ///         This can be either a literal, non-localized string provided to <see cref="NullDisplayText" /> or the
        ///         localized string found when <see cref="NullDisplayTextResourceType" /> has been specified and <see cref="NullDisplayText" />
        ///         represents a resource key within that resource type.
        ///     </para>
        /// </summary>
        /// <returns>
        ///     When <see cref="NullDisplayTextResourceType" /> has not been specified, the value of
        ///     <see cref="NullDisplayText" /> will be returned.
        ///     <para>
        ///         When <see cref="NullDisplayTextResourceType" /> has been specified and <see cref="NullDisplayText" />
        ///         represents a resource key within that resource type, then the localized value will be returned.
        ///     </para>
        ///     <para>
        ///         When <see cref="NullDisplayText" /> and <see cref="NullDisplayTextResourceType" /> have not been set, returns <c>null</c>.
        ///     </para>
        /// </returns>
        /// <exception cref="InvalidOperationException">
        ///     After setting both the <see cref="NullDisplayTextResourceType" /> property and the <see cref="NullDisplayText" /> property,
        ///     but a public static property with a name matching the <see cref="NullDisplayText" /> value couldn't be found
        ///     on the <see cref="NullDisplayTextResourceType" />.
        /// </exception>
        public string? GetNullDisplayText() => _nullDisplayText.GetLocalizableValue();
    }
}